the locate command
So you need to use a program or a file that isn't in yours or another user's directory, but you can't remember where it is. The locate command can help you find it! Type:
$ locate (file/program name) such as
$ locate acroread or
$ locate perl
The above commands will list every file with the word acroread or perl in it. This can sometimes be a lot to search through. So you might want to pipe it into less, which lets you view the output one screen at a time:
$ locate perl | less
And remember, this doesn't search the user files, so if it's in your CS21 folder, you won't find it with this command (try find ~ | grep whatever).
If locate is giving you too much output, look at the Directory List. It might give you an idea of where to look.
To find our more about locate, try man locate.